In biological filtration it is known to use various systems functioning aerobically or anaerobically, such as fixed or fluidised bacteria beds, biodiscs and activated sludge processes.
The document FR-A-2,565,579 has proposed an installation for the treatment of waste water by microorganisms, in which installation the treatment microorganisms are absorbed on glass fibres assembled in the manner of a cylindrical brush; they can be desorbed therefrom by mechanical action, which regenerates the treatment members.
The use of glass fibres and their assembly in the form of a cylindrical brush makes this type of installation costly, without any guarantee of easy accessibility to the bacteria bed formed.
The document DE-A-3,110,859 describes multiple-use devices, in particular for exchanges of materials, comprising spiralled plates.
The document CH-A-621,263 describes a device for treating liquids with gases, comprising a conduit containing metal shavings or plastic materials.
All these systems offer only a small fixation surface for the bacterial film relative to the weight of the support used, or they require heavy infrastructures. Their servicing in the event of blockage is difficult, given their great volume and their lack of internal accessibility.